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4BD1T manual transmission options

I think like everyone else here wanting to do a swap is on the fence over the 4BT and the 4BD1T. I'm just seeing what my options are for a manual transmission, because I know a 4BT has a lot of transmission options. Could I use the adapter from the isuzu swap kit with a manual instead of a GM auto? does anybody know if they sell an adapter to a GM manual? I like the Isuzu because they seem to be easier and cheaper to find then the cummins, they're better on fuel and from what I've read they have just as much tweaking potential as the cummins. thanks a lot.

Depends on what you are considering putting it into. If it a 2wd truck, consider using the Isuzu 5-speed. You have to be aware that US ones did not have overdrive so you will have to adjust your diff gearing/tire size accordingly. Also, you will have to deal with fabing a shift lever as the Isuzu transmissions were connected to the shift lever by a rod arrangement or cables. Remember, the cab on these tilted and the driver sits over the engine so the transmission is actually back under the bed of the truck.

You could also use an Isuzu 5-speed in a 4x4 if you had a divorced T-case.

Dieseltim on this forum has an adapter for the Dodge NV4500. It does require that you obtain an Isuzu manual flywheel and the manual transmiossion bellhousing. If you scrounge these parts, you will most likely also end up with the Isuzu transmission.

Dieseltim's adapter is probably the best way to adapt a non-Isuzu manual transmission to these engines. However, you're limited to an NV4500 with a Dodge input shaft -- anything straight from GM will have too short an input shaft.

My friend and I machined an adapter to mate an SM465 to a 4BD2-TC. It would have required two flywheels due to the GM clutch dimensions, but all that rotating mass was no worse than a stock Isuzu torque converter. As luck would have it, I got a smoking deal on a genuine GM-to-Isuzu bellhousing adapter. It's the only sure-fire way to adapt a Saginaw transmission to these Isuzu diesels, but the adapter hasn't been produced in the last 20-odd years and is very difficult to find.

Here is a picture of my custom adapter, as well as the pseudo-OEM version.

Ok cool, so your not too limited with the isuzu engine for manual transmission options. I'm planning to put together a 1974-1985 F150 extended cab, it will most likely be 2wd, I would like 4wd but if it's too complicated then I'll scrap the idea. But a manual transmission is a must in my vehicle, I don't like the slushy feeling of an auto, and I love banging through the gears and the response from the engine.

Isuzu/ NV4500 tranny

I have all the machine work done and it is now a bolt up to install an NV4500 tranny behind the 4bd1t / 4bd2tc engines. You will need an NV4500, 2 or 4x4, and the bellhousing from an Isuzu 5speed ( this will need some machine work ). You will also need an Isuzu manual flywheel and clutch pressure plate.

Our kit includes the custom clutch disk, pilot bearing, and the adapter plate.

That sounds pretty awesome, I'll keep it in mind when i eventully start my project, which will hopefully be in a few months, I am still saving up and putting together a game plan/researching so this conversion goes together, instead of it being a total disaster. thanks everyone for all the help.

Clutch/Shifter Questions

Dieseltim & some of the other Isuzu guys on this forum -

Though this is my first post, I've been lurking around here for a while looking at diesel options for some of our older gas trucks. I like the Isuzu motor, we had a couple of NPR's back in the late 80's and early 90's, they were good, efficient engines that would handle pretty much anything we asked of them.

My initial application would be a '74 Ford F250 4wd, which currently has a 360FE, NP435 4spd trans and a divorced NP205 transfercase. My transmission options are wide open if I can figure out how to shift it and work the clutch.

Regarding the Isuzu manual transmission options mentioned in this thread, I was wondering:

Assuming that you use a hydraulic clutch with the NV4500 option, what master/slave setup do you use? Dodge? Isuzu? Other?

In the alternative, how is the clutch on the Isuzu manual transmissions worked? I am assuming it is hydraulic as well - is this correct? Finally, I've read several posts which suggest that a shifter can be fabbed up for both the cable and rod shifted Isuzu transmissions. Has anyone actually done this and, if so, what kind of solution was required?

It seems to me that the NV4500 option has a major advantage in simplicity because of the shifter, but the Isuzu transmission is going to be substantially cheaper - if, and it's a big if, you don't have to change axle gears to keep RPM's down (stock axles in my F250 are 4.10).

Though this is my first post, I've been lurking around here for a while looking at diesel options for some of our older gas trucks. I like the Isuzu motor, we had a couple of NPR's back in the late 80's and early 90's, they were good, efficient engines that would handle pretty much anything we asked of them.

My initial application would be a '74 Ford F250 4wd, which currently has a 360FE, NP435 4spd trans and a divorced NP205 transfercase. My transmission options are wide open if I can figure out how to shift it and work the clutch.

Regarding the Isuzu manual transmission options mentioned in this thread, I was wondering:

Assuming that you use a hydraulic clutch with the NV4500 option, what master/slave setup do you use? Dodge? Isuzu? Other?

In the alternative, how is the clutch on the Isuzu manual transmissions worked? I am assuming it is hydraulic as well - is this correct? Finally, I've read several posts which suggest that a shifter can be fabbed up for both the cable and rod shifted Isuzu transmissions. Has anyone actually done this and, if so, what kind of solution was required?

It seems to me that the NV4500 option has a major advantage in simplicity because of the shifter, but the Isuzu transmission is going to be substantially cheaper - if, and it's a big if, you don't have to change axle gears to keep RPM's down (stock axles in my F250 are 4.10).

Thanks for any help, this is a great forum.

All the Isuzu NPR trucks use a hydraulic clutch. The slave cylinder is mounted on the bellhousing.

I'm not sure how the stock Isuzu clutches are set up, but you could always use a hydraulic throwout bearing. They're pricey, but the only component you need to worry about is the clutch master cylinder. I bet a company like McLeod could even do custom applications.

rakent, keep in mind that the U.S spec 5 speeds are all direct 5th (no o.d).With 4.10 gears you will want a overdrive.

You can compensate for this with a change in diff gearing and/or larger tire size. For example, if your diff is a 4.10 ratio, tire diameter is 31" and your were considering an NV4500 swap (0.75 5th gear), you could accomplish the same using a direct 5th gear transmission and changing to 3.23 diff ratio and 33" diameter tires. This may be a significantly less expensive option than acquiring a NV4500 along with all the required parts and adapters.

You can compensate for this with a change in diff gearing and/or larger tire size.

Following what astr suggested, if you're concerned about performance off-road, remember that these diesels generally do not require steep gearing like a gas motor. They produce torque at a lower engine speed, so extra gearing isn't necessary to slow the vehicle down whilst off-road.

My Jeep, for example, is geared with a 3.55 axle ratio and I'll be running 35" tires. Most rigs like this are set up with 4.56+ ratios, but it's not really necessary with a diesel engine. Although steeper gears would have increased torque multiplication, it would have been difficult to drive it on the highway. As it stands, cruise is right around 2000 rpm at 60 mph, with a maximum top speed of 80 mph at 2800 rpm. No overdrive, either.

I'm not sure what vehicle the adapter came in... I don't even know if they were ever offered like that. Dougal sent me some literature a few weeks ago that provides evidence that the GM adapters were aftermarket pieces, and maybe not even made by Isuzu.

adapters

From the best I could tell in my hunt. The 4bd (non-turbo) engines were the only ones to come with anything that would bolt up to a gm or ford tranny most of these were industial units (not for road use), and they are really hard to find. When the 4bd1t engine came out it had the metric isuzu pattern. That was the whole reason that I designed and built the adapter that would allow the use of the NV4500 ( gm or dodge) tranny. It is a tough, easy to find and strong tranny. It comes in 2 and 4x4 and had many different options for tranfer cases.

For those of you that Still have to have an Automatic, I am looking for the right unit to build an automatic adapter kit as well. Just give me some time to find one that has OD and a removable bellhousing and that can be found in large enough numbers for widespread useage. Don't hold your breath I have been looking for some time already.

How safe is the dual flywheel system? Like could it take a beating, and hold up? dieseltim can you redrill the bellhousing for a tranny other then a nv4500? what kind of flywheel do you use for your type of conversion?

How safe is the dual flywheel system? Like could it take a beating, and hold up?

The adapter I was working on would have used two flywheels. From my calculations, it shouldn't have made a difference. A GM flywheel, pressure plate, clutch, and adapter would have about the same mass as an Isuzu torque converter (55 lb). It's also not nearly as long, which should put less bending stress on the crankshaft. Unfortunately, these are all just estimates -- I don't have a working model yet.

other trannys

83stang
The main reason for using the NV4500 tranny is that it has a longer input shaft than anything else that I could find. I needed the longer shaft to have room to make the adapter plate. The bolt pattern is not the problem it is a matter of spacing.

tranns in isuzu

Hi hoping to get info myself on this swap i just picked up a 1997 npr turbo (diesel powerd) compleat from a tow yard in sacramento with a blown auto tranny i want to swap into my 1971 fj40, i have the chance to pick up a bell housing from a 80/84 6bd1 bread van with a borg warner t-18 trans on it im hopeing the bell housing pattern will be the same and hook it up to my beloved SM-420 any info would be great.

Hi hoping to get info myself on this swap i just picked up a 1997 npr turbo (diesel powerd) compleat from a tow yard in sacramento with a blown auto tranny i want to swap into my 1971 fj40, i have the chance to pick up a bell housing from a 80/84 6bd1 bread van with a borg warner t-18 trans on it im hopeing the bell housing pattern will be the same and hook it up to my beloved SM-420 any info would be great.

I'd be very interested to know if the bell housing from the Isuzu 6bd1 bolts up to the 4bd2. Let us know one way or the other.

In case anyone is interested, I fitted up the "sort-of-OEM" SAE adapter to my 4BD2. I mentioned previously that these adapters were apparently offered for industrial applications, but Dougal has shown they were available as aftermarket pieces, presumably from a third-party manufacturer. I'm not sure where mine came from.

The first thing that needs changed is the engine adapter. This converts the back of the motor to an SAE #3 bolt pattern, complete with 3/8" UNC threaded holes. The stock 4BD2 adapter is on the left... note that the rear main seal is integral to the SAE adapter. (Is this normal for the older Isuzu diesels?)

In order to get this to fit on my 4BD2, I had to remove the two dowel pins for the previous seal assembly (arrows).

Here it is all bolted up. Hopefully I'll have the transmission mounted tomorrow.

Good work 86/others. Now here's a question for you learned people. Will both those bellhousings bolt up to all 4bd1/2 and their turbo brothers. And does it matter the seal is in the sae unit or can u just delete the normal seal unit n still bolt the sae on and it's all good.. sort of, either will fit if you use the respective parts... thnks again

If I lived closer I'd be on that spare housing like a fly on a cowpat..

Will both those bellhousings bolt up to all 4bd1/2 and their turbo brothers. And does it matter the seal is in the sae unit or can u just delete the normal seal unit n still bolt the sae on and it's all good.. sort of, either will fit if you use the respective parts... thnks again

Well, my SAE adapter came off a 4BD1, and I'm using it on a 4BD2. The engine adapter bolt pattern (in the block) is the same, so the castings are interchangeable. Only thing you gotta do is remove those two dowel pins I mentioned above.

Fitting up a clutch fork and throw-out bearing with the SAE adapter is another story, though. I'm not sure if I have a messed up casting, but the hole for the fork is not centered with the pivot ball. You'd either need to enlarge the hole (and ruin any chances for fitting a rubber boot), or find a thinner fork. I'm going down a different route with a hydraulic throw-out bearing, but even that requires some modification.

I'm going to test-fit the transmission again this afternoon and get back with some pictures.

Dougal, on the drawing of your Isuzu I note you show two bolts for the starter, I also note on 86s fotos of the mounting housing, they show 3 bolts for the starter. Is/could this be because yours is for 12v and 86s are for 24v. Do you have any info on this anomaly/variation... thnks

Dougal, on the drawing of your Isuzu I note you show two bolts for the starter, I also note on 86s fotos of the mounting housing, they show 3 bolts for the starter. Is/could this be because yours is for 12v and 86s are for 24v. Do you have any info on this anomaly/variation... thnks

My starter is a 12 V unit. The two batteries are wired in parallel, not series. I figure Isuzu did this to double up on the supply of current.

Dougal, on the drawing of your Isuzu I note you show two bolts for the starter, I also note on 86s fotos of the mounting housing, they show 3 bolts for the starter. Is/could this be because yours is for 12v and 86s are for 24v. Do you have any info on this anomaly/variation... thnks

It seems to be an enigma.
The US versions that I've seen photos are all 3 bolt starter and 12 volt. The Australian 4BD1's (not factory turbo) fitted to landrovers have a 3 bolt starter and are 12 volt. My engine was a JDM (japanese domestic market) version with 24v ancillaries, 2 bolt starter and single belt driving the water pump and alternator.